queue / max_queue metrics returns invalid values for UNIX domain sockets

[sylvain-morin]

When we configure UWSGI to use UNIX domain sockets (unlike TCP socket), the queue and max_queue metrics are always equals to 0.

"sockets":[
		{
			"name":"/home/uwsgi/socket",
			"proto":"uwsgi",
			"queue":0,
			"max_queue":0,
			"shared":0,
			"can_offload":0
		}
	]

@pinaraf implemented a fix for this issue: #2493

When runnning UWSGI from this branch, the metrics are correct, reflecting the load we are generating.

[pinaraf]

Regarding #2493, please note this patch is dirty and not that efficient, I would not run it as is in production, but I did not go any further due to the lack of interest here (and we thus, sadly, switched to TCP instead of UNIX sockets).
If you want to run uwsgi with this kind of feature, I may find some spare time and improve the patch, but considering the current status of uwsgi (more or less "fixes only, no new developments") I doubt this would ever go upstream :/